Question 643881

I have done 7/10 of my homework. I will submit each one separately. 
The answers are randomized on the back, but it seems as if they aren't correct.
#6. The total surface area of a can is 188.4 in squared. If the radius of the can is 3 inches. what is the height of the can?

I tried, s=2 times pi times 3 times height plus 2 times pi times 3 ^2


You are correct!! S, or surface area of cylinder (can) = {{{2*pi*r^2 + 2*pi*rh}}}
This gives us: 


{{{S = 2*pi*r^2 + 2*pi*rh}}}


{{{188.4 = 2*pi*3^2 + 2*pi*3*h}}}


{{{188.4 = 2*pi*(9) + 6*pi*h}}}


{{{188.4 = 18*pi + 6*pi*h}}}


{{{188.4 - 18*pi = 6*pi*h}}}


{{{h = (188.4 - 18*pi)/(6*pi)}}}


{{{h = 6(31.4 - 3*pi)/(6*pi)}}}


{{{h = cross(6)(31.4 - 3*pi)/(cross(6)*pi)}}}


{{{highlight_green(h = (31.4 - 3*pi)/pi)}}}, or


h, or height of can = 6.99493 ≈ {{{highlight_green(7)}}} inches


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